Soft stone eliminator



Jan. 17, 1939. MIKAN 2,144,384

SOFT STONE ELIMINATOR Filed Dec. 27, 1933 2 Sheets-Sheef; 1

o o O O 4 We for Ni/ran Jan. 17, 1939.

v. MIKAN SOFT STONE ELIMINATIOR 2 Sheets-Sheet 2 Filed Dec. 27, 1953 Viefor Mike/7 Patented Jan. 17, 1939 UNITED STATES PATENT OFFICE sor'rSTONE ELIMINATOR' Victor Mil ran, Durand, Mich. V ApplicationDecember27, 1933, Serial No. 704,156

3 Claims.

This invention relates to a machine and to a method for the reduction ordisintegration of soft particles present in a mixture of soft and hardparticles to permit the separation of onemechanical eliminators arebuilt on the principle of throwing the individual stones against a wallor plate with sufficient force to cause the soft stone particles tobreak. In the theory and practice this design is incorrect, and it visusually found that quite ahigh percentage of good stone is reduced andrendered unfit. The reason is, that the kinetic energy, in the'thusthrown stone, is a function of its mass, and the hard stone beingheavier than the .soft stone, 9. large portion of the good or hard stoneis thrown with sufficient force to reduce the same to an objectionableextent during the reducing of the soft stone. A further undesirablefeature of these machines is that the impact which the individualparticles receive is wholly uncontrolled. A still further undesirablefeature is that due to the inherent design of the machines of this type,replacements of wearing parts are frequent and usually quite costly.

It is an object of ,this invention to. eliminate 7 the above undesirablefeatures and to provide a machine which will readily and effectivelyelim- A still further object of this invention is to provide anew methodof eliminating soft stone from gravel, which consists in subjecting thegravelto. a series of impacts of controlled intensity'to break the softstone and to render the gravel suitable. for separating the 'broken'soft(cl. act-#94) stone from the hard stone by screening or the like.

These and other objects will be apparent when taken with thespecification and accompanying drawings in which,

Fig. 1 is a perspective view of Fig. 2 is a side elevation,

Fig. 3 is a vertical section taken on theline III-III of Fig. l,

the invention,

Fig. 4 is a vertical section taken on line IV--IV of Fig. 2, and

Fig. 5 is a vertical section taken on the central axis of an impact bar.

The soft stone eliminator I is mounted on a supporting frame 2. Theprinciple element of the invention is the rotor 3 which consists ofimpact bars 4, a mounting plate 5 and an annular plate ii. The mountingplate 5 is sup,-

ported and attached to a flanged hub I which plates into which they arefitted, as at l2. The

impact bars 4 are prevented from rotating on their own axes by lugs l3fitting in small bores M. It has been found that there is a greatamount. of wear on the inside faces of the impact bars 4 and practicallynone on the outside faces. The impact bars 4 are therefore designed asshown in Fig. 4 heavily built up on-the wearing side. To the inside ofthe mounting plate-.5 is attached a deflecting ring if: to deflect thegravel which enters the machine ,through'the hopper IE to the impactbars 4.

The rotor 3 is enclosed in front by plates I1,

and i8 and in the rear by plates Hand 20. Between the front andrearplates the casing'casting 22 is mounted by means of bolts M. The

casing casting 22 surrounds substantially the en-' tire periphery of therotor 3 and with the plates l1 and 20 defines the exit chute 23 throughwhich 'treated gravel is discharged onto a sizing screen not shown, orinto any suitable container. The plates l1 and IB are constructed with asuitable opening to permit the reception and attachment of the hopperl6.

' The operation is as follows: Gravel containing soft stone isintroduced to the. machine through the hopper I6. It strikes thedeflecting ring [5 and is deflected downwardly to the impact bars 4,which" are rotating with the rotor 3, and the individual particles arestruck one or more blows. The characteristics of the hard and soft stonein the gravel will vary with each gravel pit and for this reason it isnecessary to regulate the peripheral speed of the rotor until asatisfactory reduction in soft stone is accomplished. By reg ulating therate of rotation of the rotor the intensity of the impact of the bars 4may be controlled to the point that substantially all the soft stone isreduced without breaking up the good or hard stone to any objectionableamount. In'

, some cases it may-even be desired to increase the speed of the rotor 3to the point where the hard stone is reduced to a controlled degree toimprove its characteristics for certain types of construction work. Inpractice it has been found that with most grades of gravel rotation of a36 inch rotor between 475 to 600 revolutions per minute will resultirr'the reduction of soft stone in the gravel to less than 1% withoutobjectionable reduction of good or hard stone. Following impact by thebars 4, the gravel is carried by its own velocity and in some cases byadditional impacts out against the casing casting 22. From there it iscarried around the rotor 3, bearing heavily, due to centrifugalforce'against the casingcasting 22 and is discharged unharmed out of theexit chute 23. -In the event that a soft piece of stone drops throughthe hopper l6 into the machine it is struck one or more blows by theimpact bars 4. Usually theflrst blow breaks the soft stone into manysmaller pieces, and these pieces are carried through in the same manneras the good stone. The blows of the impact bars 4 and the abrasiveaction of the casing casting 22 on the soft stone particles as they arecarried around between the casing casting 22 and the rotor 3, togetherwith the scrubbing action they receive from the other pieces of stone inthe machine disintegrates or reduces them to.

stantiated. The particles appearto be given sev- I eral impacts beforethey leave the confines of the rotor and casing casting. While it isbelieved that the particles rebound to a certain extent, between therotor 3 and the casin this theory is not wholly borne o by theappearance of the machine after continued use, for there is practicallyno wear on the outsides of the impact bars 4. It has been found that thebest results are obtained when water is admitted to the machine with thegravel, the water reducing wear and assisting in the removal of brokendown or disintegrated soft stone.

A novel and important feature of this invention is the operation of thedeflecting ring IS in conjunction with the impact bars 4. When thedcfiecting ring is new, its shape causes it to deflect 4 the gravel to apoint on the impact bars 4 near casting 22,

the gravel to a point on the impact bars nearer life of the impact barsis considerably lengthened. That my improved method of disintegratingthe soft stone can. be carried out in apparatus other than the oneheretofore described is fully'appreciated. The essential features residein directing a stream of gravel containing both hard and soft stone withrelatively slight velocity into a region where both the hard and softstones are acted upon by impact members or equivalent means havingconsiderable velocity with equal intensity; the kinetic energy of theimpact members being so controlled as to result substantially only inthe disintegration of the soft stone without breakage or reduction ofthehard or good stone beyond an objectionable amount. In this respect mymethod varies from other methods employed in similarv machines in whichthe kinetic energy of the gravel itself is utilized to disintegrate thesoft stone.

By gravel, small stones having a diameter ofv not greater than. threeinches, is meant. The soft stone referred to may be either separate orattached to hard or good stone, and'includes, for

-to the operation and characteristics of my. ma-

chine and improved method of removing soft stone from gravel applyequally as well in the reduction of soft particles in other mixtureswhere ,it is desired to so reduce the soft particles to permitseparation from hard particles by screening or equivalent methods. Forexample, my improved apparatus and method has application in thereduction of rock saltto permit the hard shale present to be separatefrom the salt by screening. Also in the refining of gypsum being softerthan the dolomite, the latter may be separated by screening upon thereduction of the softer particles of gypsum.

In the claims the referenceto gravel and the like is used to designategenerally mixtures of hard and soft particles including besides gravelother mixtures having similar characteristics including' thosespecifically mentioned in the foregoing paragraph. I

While the specification discloses a single embodiment of the inventionit is apparent that it is merely illustrative of the broad principlesin- V.olved and it is not intended that it be limited except by thescope of the following claims.

I claim:

1. A method of processing gravel used asan aggregate in concreteconstruction to reduce the soft stone commingled with the gravel to a"fineness permitting separation by screening or washing comprising,directing a stream of gravel downwardly to flow by gravity, subjectingsubstantially all the particles in the flowing stream of gravel toimpact blows of substantially uniform intensityapplied transverselyacross the line of flow by moving a series of impact members in singlefile in the same direction across the line of flow, regulating theintensity of such blows so that the force of such blows will besufficient to disintegrate soft particles without appreciable fracturingof hard particles, further treating the gravel and soft stone by saidimpact members to effect a rubbing and abrasive action thereon andsimultaneously discharging both hard and soft particles. x

2. 'I'he method of processing gravel for use as an aggregate in concreteconstruction which gravel consists of hard stone pieces capable ofbearing load forces encountered in use and soft stone pieces likely tobreak down under load forces of use comprising, directing a stream ofsuch gravel to travel in a predetermined path and at substantiallyuniform speed, and subjecting substantiallyall of the stone pieces inthe stream of gravel to impact blows of substantially uniform intensityapplied transversely across the line of flow by moving a series ofimpact members in single file in the same direction across the line offlow and regulating the intensity of such blows so that the force of theblows is sufficient to disintegrate soft stone pieces withoutappreciable fracture of hard stone pieces.

3. The method ofprocessing gravel for use as .an aggregate in concreteconstruction which gravel consists of hard stone pieces capable ofbearing load forces encountered in use and soft stone pieces likely tobreak down under load forces of use comprising, directing a stream ofsuch gravel to travel in a predetermined path and at substantiallyuniform speed, subjecting substantially all of the stone pieces in thestream of gravel to impact blows of substantially uniform intensityapplied. transversely across the line of flow by moving a series ofimpact members in single 'flle in the same direction across the line offlow and regulating theintensity of such blows so that the force of theblows is sufficient to disintegrate soft stone'pieces withoutappreciable fracture of hard stone pieces, and confining the materialfollowing the application of the impact blows to travel with theunfractured hard stone pieces and the fractured soft stone particlesintermixed and discharging the same through an outlet.

vicroa MIKAN.

